HNC Electrical Eng Maths Unit HELP!

Hi all,

First post here. I'm currently studying an HNC in Electrical / Electronic Engineering.

Maths has always been my weakness and I'm stumped on a question:

The curve assumed by a heavy power cable is described by the equation...
y = 60 cosh (x/60)

Calculate:
(i) The value of y when x is 104
(ii) The value of x when y is 180

for (i) I've literally plumbed into my calculator 60cosh(104/60) = 175.08

However I have no idea where to start with (ii).. any advice would be great

Answer to first part should be 175.09 if you're going to round it to 2dec.pl.

I'll use acosh for the inverse of the cosh function.

If we rearrange our function we get:

y/60 = cosh (x/60)

So, x/60= acosh (y/60) and x = 60 acosh (y/60)

(I am assuming you only want the postive x value. Cosh is symmetric about x=0, so any inverse can be +/- the particular value.)

Since you've used a calculator for the first part, I presume you can do the same for the second.

Yes, the question hints about using a calculator in RAD mode.

That makes a little more sense. It does mention with X and Y horizontal and vertical respectively so I'm assuming, unless I'm misreading the question, it also wants it plotted?

I wouldn't do a plot unless specifically requested, but my background is maths rather than electrical engineering. You could post an image of the original question, and it might be clearer.

Hope it has attached correctly

Answer to first part should be 175.09 if you're going to round it to 2dec.pl.

I'll use acosh for the inverse of the cosh function.

If we rearrange our function we get:

y/60 = cosh (x/60)

So, x/60= acosh (y/60) and x = 60 acosh (y/60)

(I am assuming you only want the postive x value. Cosh is symmetric about x=0, so any inverse can be +/- the particular value.)

Since you've used a calculator for the first part, I presume you can do the same for the second.

Hello i get y to be 175.09 and x to be 14.36 ? years since i was at collage , currently offshore construction superintendent studying my HNC could you please let me know if am on the right track

y-value is fine to 2dec.pl. x-value is in error. Post your working if you've like someone to check through what you're doing.

Edit: As a check you could plug that x-value back in to see if you get y equal to 180.

Sorry for the late reply , i have just spent the last 3 weeks on an oil rig in the middle of the northsea. Thank you so much for all your assistance and i after a bit of a struggle finding the correct functions on my calculator i got the x-value to x =60 acosh(180/60) =105.76

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